Burners

ABSTRACT

A liquid fuel burner having a burner element in the form of a plurality of ducts for the supply of one combustion component, a second combustion component being supplied from the regions between the ducts, the burner having heat conductors to transmit heat from the burner to a vaporization chamber in which liquid fuel is vaporized for supply to the burner element.

United States Patent Ware 51 Aug. 1, 1972 [54] BURNERS 1,676.080 7/1928 Davis....L ..431/242 Inventor: Peter G. w g y, England DCSty et al [73] Assignee: Dunlop Holdings Limited, London, Primary Examiner-Edward G. Favors E l d Attorney-Stevens, Davis, Miller & Mosher [21] PP N04 73,013 A liquid fuel burner having a burner element in the form of a plurality of ducts for the supply of one combustion component, a second combustion component [2?] :LS. (g1. ..i gdsi/lzljz being supplied from the regions between the ducs the nt. burner having heat conductors to transmit heat from [58] Fleld of Search ..431/11, 242,243, 247 h butner to a vaporization chamber in which liquid fuel is vaporized for supply to the burner element.

[56] References Cited 6 Claims, 4 Drawlng Figures UNITED STATES PATENTS 674,345 5/1901 Skerry ..431/242 BURNERS This invention relates to burners, and particularly to burners for liquid or gaseous fuels of the kind described in the specification of my co-pending U.S. application Ser. No. 53,104 filed July 8, 1970.

In the specification of US. application Ser. No. 53,104 a number of burner element constructions are described which comprise in general a first sheet member and a second sheet member arranged in superimposed relationship with one another, the sheet members each having a plurality of apertures, the apertures in the respective sheet members being in superimposed relationship with one another and the material of the first sheet member surrounding each of the apertures therein extending as a tubular projection into the associated aperture of the second sheet member.

The first sheet member may be a perforated metal plate arranged beneath a correspondingly perforated second sheet member formed from porous metallic or ceramic material for example of the kind which is in the form of a three-dimensional network arranged to define a plurality of cellular spaces which communicate with one another.

A particularly suitable porous metallic material of the kind described above, having the characteristics of good durability at high temperatures is the chromium alloy produced by the methods described in the specifications of the assignees co-pending US. Pat. application Ser. No. 847,428 filed Aug. 4, 1969 and Ser. No. 50,383 filed June 29,1970.

In a burner element of the kind described, the sheet members are spaced to form a gallery for the supply of liquid or gaseous fuel, while the apertures provide passages for combustion air.

It has been found that burner elements of the kind described above are particularly successful in burning gaseous fuel but are less successful in burning liquid fuels for reasons including a tendency for carbon to form on the porous sheets. I

One object of the invention is to provide an improved burner, incorporating a burner element of the general kind described above, which is particularly suitable for burning liquid fuels.

According to one aspect of the present invention, a burner for liquid fuel comprises in combination a fuel supply means comprising a vaporization chamber to which heat is transmitted from the combustion zone of the burner in operation thereof, and a burner element in which a plurality of apertures are formed in an upper sheet, a fuel supply gallery being formed between said upper sheet and a lower sheet through which ducts for the supply of combustion air to the apertures are arranged to pass, the fuel supply gallery being provided with means for the supply of fuel to the combustion zone.

According to a further aspect of the invention, a burner for liquid fuel as described in the preceding paragraph comprises a vaporization chamber wherein at least one heat conducting member extends from the vaporization chamber over the surface of the burner element to conduct heat from the combustion zone to the vaporization chamber in operation of the burner.

According to a still further aspect of the invention a burner for liquid fuel as described in the second preceding paragraph comprises a vaporization chamber wherein a plurality of heat conducting'members are arranged to extend through the ducts to conduct heat from the combustion zone to the vaporization chamber in operation of the burner.

The heat conducting members may be in the form of spikes formed from a metal having adequate heat conducting and oxidation resisting properties, such as steel, and the spikes may conveniently be mounted so as to pass coaxially through the associated ducts to conduct heat from the combustion zone into a primary fuel supply gallery containing liquid fuel so as to vaporize the fuel, the primary fuel supply gallery being arranged to be connected to a secondary fuel gallery through which fuel vapor driven off from the primary gallery by the conducted heat may be supplied to the combustion zone.

Three embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a sectional elevation of a burner comprising a matrix of spikes;

FIG. 2 is a diagrammatic perspective view of another form of burner according to the invention;

FIG. 3 is a plan view of a further form of burner according to the invention and FIG. 4 is a side elevation of the burner shown in FIG. 3, partly in section along the line XX of F IG. 3.

In a first embodiment of the invention (illustrated in FIG. 1), a burner element 1 is constructed as follows.

A sheet 2 of porous metallic material of the kind described is provided by spraying, dipping or electrodeposition of a metal on a polyurethane foam material. After deposition of the metal the polyurethane foam is removed by heating to ash-out the polyurethane. The polyurethane foam used is of the reticulated form, i.e., a foam in which the organic phase is a three-dimensional network with no substantial wall portions defining the cells, and the porous metallic material produced by the process outlined above has the property that it contains intercommunicating cells through which fuel in gaseous form can pass.

' The sheet 2 is assembled in superimposed relationship with a metal backing plate 3 which is dome-shaped and lies within a dome formed by the sheet of porous material and an annular sheet-metal collar 4 welded to the edge of the sheet.

The assembly is pierced by holes 5, having a diameter of 0.1 to 0.15 of an inch, punched from below the backing plate 3, and passing through the sheet 2 of porous material. The material of the backing plate is swaged by the punching operation to form a lining 5a for each hole extending partly through the porous sheet.

The burner element thus comprises a sealed fuel supply gallery 6, being a secondary supply gallery, formed between the backing plate and the porous sheet and collar. Air for combustion is supplied through the holes 5 formed by the punching operation, and is sealed from the fuel supply gallery by the metal of the backing plate which has been swaged into the holes.

A perforated metal support member 7 is secured at its outer edge 8 to the edges of the collar 4 and the backing plate 3 and extends below the perforated .12 entering the apertures in the support member 7, the

upper ends of the projections being soldered or otherwise sealed into the apertures to form a fluid-tight gallery between the support member and the lower backing plate.

The arrangement is such that combustion air can pass upwardly through the apertures formed in the primary supply gallery, and through the annular gaps formed between the spikes and the surrounding walls of their respective ducts. I

At the outer peripheral edge 8 of the primary supply gallery a number of apertures or pipes 13 lead into the secondary supply gallery 6. In operation, liquid fuel fed through an inlet pipe 14 into the primary supply gallery is vaporized .by heat conducted thereto through, the stainless steel spikes which extend at their upper ends into the combustion zone 15, and passes as a gas into the secondary supply gallery from which it is fed through the porous sheet to the combustion zone.

In addition to conducting heat to the primary fuel supply gallery, the spikes have the further property of pre-heating the combustion air as it passes through the burner element.

A further property of the spikes is that they confine the flow of air through each duct to the regions adjacent the edge of the duct, and this assists in producing a more homogeneous mixture of the air: passing through the duct with the gas emerging from the surrounding portions of the porous sheet.

In a second embodiment (illustrated in FIG. 2) a sheet 1 of porous metallic material of the kind described with respect to the first embodiment is assembled in superimposed relationship with a metal backing plate which is dome-shaped and lies within a dome formed by the sheet of porous material and an annular sheet-metal collar 2 welded to the edge of the sheet.

The assembly is pierced by holes 3, having a diameter of 0.1 to 0.15 of an inch, punched from below the backing plate, and passing through the sheet of porous material. The material of the backing plate is swaged by the punching operation to form a lining for each hole extending partly through the porous sheet.

Fuel supply means for the element 4 described above comprises a length of metal piping 5 arranged to be connected to a fuel supply so that liquid fuel, which may be a heavy gas oil, is fed to a vertically aligned portion of the pipe adjacent the burner element 4 and arranged to form a vaporization chamber 6. The vaporization chamber is arranged to be heated at its upper end by suitable metallic conductors 7 extending into the combustion zone, while the lower end is kept cool, partly by the flow of fuel 8 and partly by surface radiation. From the upper part of the vaporization chamber a pipe 9 extends in spiral or zig-zag fashion above the surface of the burner to form a superheating or drying chamber and is then taken downwardly to a connection 10 to the fuel supply gallery formed between the sheet of porous metallic material and the metal backing plate. At the connection point the superheated fuel vapor enters the gallery through a control orifice 11, the size of which is controlled by a conventional needle valve. In operation, once the burner has been raised to the required temperature, for example by electrical heating, the heat from the burner maintains a high temperature at the top of the vaporization chamber 6 and the liquid fuel vaporizes at the meniscus of the liquid fuel in the vertical part of the chamber and passes as a hot dry gas into the fuel supply gallery. From the gallery, the gas passes to the combustion zone where it is mixed with air drawn upwardly through the apertures described above to produce a silent, evenly burning flame.

Control of the burner described in this embodiment may be effected by adjustment of the needle valve, and this may be operated automatically by means of an electrical solenoid and suitable apparatus.

In a third embodiment of the invention (illustrated in FIG. 3 and FIG. 4) a rectangular burner element 1 of the kind described with respect to the preceding embodiment is supported within a support structure 2 comprising four walls arranged around the periphery of the burner element and extending above the upper surface 3 of the burner element.

A fuel supply pipe 4 for the supply of fuel to the burner element enters the burner through an aperture 5 in a wall of the support structure and extends upwardly around the periphery of the burner element, above the plane of the upper surface 3 of the burner element, in the form of at least one rectangular loop arranged substantially in the plane of the burner element and supported by the inner surface of the support structure. Within the support structure the looped fuel supply pipe is fitted to the inlet of a conventional needle valve 6, itself supported by the inner surface of the support structure.

Two finned tubes 7 and 8 are arranged parallel to each other and are supported by means of the support structure 2 above and substantially parallel to the upper surface 3 of theburner element. An interconnecting pipe 9 joins an end of one tube with an end of the other tube, the other end of one tube being connected by a tube inlet pipe 10 to the outlet of the needle valve 6 and the other end of the other tube being connected by an outlet pipe 11 to the fuel supply gallery formed between the two sheets of the burner element.

In operation, the heat from the burner heats the liquid fuel in the pipe loop and the finned tubes, the fuel passing as a vapor from the finned tubes through the outlet pipe to the fuel supply gallery of the burner element.

Regulation of the heat output of the burner may be effected by automatic adjustment of the needle valve as described with respect to the preceding embodiment.

The burners described above have the advantage that since the liquid fuel is converted to a vapor in the absence of air before it enters the porous sheet, the tendency for carbon to form in the burner system is reduced or eliminated.

Having now described my invention, whatl claim is:

l. A burner for liquid fuel comprising, in combination:

a burner element comprising a lower sheet and a superimposed upper sheet, said upper sheet have a plurality of apertures therein and formed with a fuel supply gallery through which ducts for the supply of combustion air to the apertures are arranged to pass, said ducts being formed between said upper sheet and said lower sheet,

fuel supply means comprising a fuel vaporization chamber,

at least one heat conducting member arranged to transmit heat to the fuel vaporization chamber from the combustion zone of the burner, and

a fuel supply pipe arrange to extend over the surface of the burner element so that fuel flowing from the fuel vaporization chamber to the fuel supply gallery is heated by heat from the combustion zone of the burner.

2. A burner according to claim 1 wherein the heat conducting member is arranged to heat an upper portion of the vaporization chamber to vaporize liquid fuel contained in the chamber.

3. A burner according to claim 1 wherein the heat conducting member extends into the region of maximum temperature of the combustion zone.

4. A burner according to claim 1 wherein the ducts through the fuel supply gallery are formed from the material of the lower sheet surrounding each of the apertures therein.

5. A burner according to claim 1 wherein the upper sheet is formed from a porous metallic material.

6. A burner according to claim 1 wherein the regions of upper sheet surrounding the apertures formed therein are provided with perforations for the supply of fuel from the fuel supply gallery to the combustion zone. 

1. A burner for liquid fuel comprising, in combination: a burner element comprising a lower sheet and a superimposed upper sheet, said upper sheet have a plurality of apertures therein and formed with a fuel supply gallery through which ducts for the supply of combustion air to the apertures are arranged to pass, said ducts being formed between said upper sheet and said lower sheet, fuel supply means comprising a fuel vaporization chamber, at least one heat conducting member arranged to transmit heat to the fuel vaporization chamber from the combustion zone of the burner, and a fuel supply pipe arrange to extend over the surface of the burner element so that fuel flowing from the fuel vaporization chamber to the fuel supply gallery is heated by heat from the combustion zone of the burner.
 2. A burner according to claim 1 wherein the heat conducting member is arranged to heat an upper portion of the vaporization chamber to vaporize liquid fuel contained in the chamber.
 3. A burner according to claim 1 wherein the heat conducting member extends into the region of maximum temperature of the combustion zone.
 4. A burner according to claim 1 wherein the ducts through the fuel supply gallery are formed from the material of the lower sheet surrounding each of the apertures therein.
 5. A burner according to claim 1 wherein the upper sheet is formed from a porous metallic material.
 6. A burner according to claim 1 wherein the regions of upper sheet surrounding the apertures formed therein are provided with perforations for the supply of fuel from the fuel supply gallery to the combustion zone. 